<template>
  <div class="pagination">
    <button :disabled="pageNo <= 1" @click="$emit('changePageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-show="continueStartEnd.start > 1"
      @click="$emit('changePageNo', 1)"
    >
      1
    </button>

    <button v-show="continueStartEnd.start > 2">···</button>

    <button
      :class="{ active: page === pageNo }"
      @click="$emit('changePageNo', page)"
      v-for="page in continuePagesArr"
      :key="page"
    >
      {{ page }}
    </button>

    <button v-show="continueStartEnd.end < totalPages - 1">···</button>
    <button
      v-show="continueStartEnd.end < totalPages"
      @click="$emit('changePageNo', totalPages)"
    >
      {{ totalPages }}
    </button>
    <button
      :disabled="pageNo === totalPages"
      @click="$emit('changePageNo', pageNo + 1)"
    >
      下一页
    </button>
  </div>
</template>

<script>
  export default {
    name: "Pagination",
    props: ["totalPages", "continuePages", "pageNo"],
    computed: {
      continueStartEnd() {
        const { totalPages, continuePages, pageNo } = this;
        let start = 0;
        let end = 0;

        start = pageNo - Math.floor(continuePages / 2);
        end = pageNo + Math.floor(continuePages / 2);

        if (start < 1) {
          start = 1;
          end = continuePages;
        }

        if (end > totalPages) {
          end = totalPages;
          start = totalPages - continuePages + 1;
        }
        console.log(start, end);
        return { start, end };
      },

      continuePagesArr() {
        const { start, end } = this.continueStartEnd;
        const arr = [];
        for (let i = 1; i <= end; i++) {
          if (start <= i) {
            arr.push(i);
          }
        }
        return arr;
      },
    },
  };
</script>

<style lang="less" scoped>
  .pagination {
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    }
  }
</style>
